Ether, polymer, resist composition and patterning process

ABSTRACT

An ether compound of formula (1) is provided wherein R 1  is H or C 1-6  alkyl, R 2  is C 1-6  alkyl, R 3  is H, C 1-15  acyl or C 1-15  alkoxycarbonyl which may be substituted with halogen atoms, k is 0 or 1, m is from 0 to 3, and n is from 3 to 6. The ether compound is polymerized to form a polymer having improved reactivity, robustness and substrate adhesion. A resist composition comprising the polymer as a base resin is sensitive to high-energy radiation, has excellent sensitivity, resolution, and etching resistance, and lends itself to micropatterning with electron beams or deep-UV.

[0001] This invention relates to (i) an ether compound, (ii) a polymercomprising specific recurring units, (iii) a resist compositioncomprising the polymer as a base resin, and (iv) a patterning processusing the resist composition.

BACKGROUND OF THE INVENTION

[0002] While a number of recent efforts are being made to achieve afiner pattern rule in the drive for higher integration and operatingspeeds in LSI devices, deep-ultraviolet lithography is thought to holdparticular promise as the next generation in microfabricationtechnology. In particular, photolithography using a KrF or ArF excimerlaser as the light source is strongly desired to reach the practicallevel as the micropatterning technique capable of achieving a featuresize of 0.3 μm or less.

[0003] For resist materials for use with a KrF excimer lasers,polyhydroxystyrene having a practical level of transmittance and etchingresistance is, in fact, a standard base resin. For resist materials foruse with ArF excimer lasers, polyacrylic or polymethacrylic acidderivatives and polymers containing aliphatic cyclic compounds in thebackbone are under investigation. All these polymers have advantages anddisadvantages, and none of them have been established as the standardbase resin.

[0004] More particularly, resist compositions using derivatives ofpolyacrylic or polymethacrylic acid have the advantages of highreactivity of acid-decomposable groups and good substrate adhesion andgive relatively satisfactory results with respect to sensitivity andresolution, but have extremely low etching resistance and areimpractical because the resin backbone is weak. On the other hand,resist compositions using polymers containing alicyclic compounds intheir backbone have a practically acceptable level of etching resistancebecause the resin backbone is robust, but are very low in sensitivityand resolution because the reactivity of acid-decomposable protectivegroups is extremely low as compared with those on the acrylic polymers.Since the backbone of the resin is too robust, substrate adhesion ispoor. These compositions are thus impractical as well. While a finerpattern rule is being demanded, there is a need to have a resistmaterial which is satisfactory in sensitivity, resolution, and etchingresistance.

SUMMARY OF THE INVENTION

[0005] Therefore, an object of the present invention is to provide (i)an ether compound capable of forming a polymer having improved substrateadhesion, (ii) a polymer having improved reactivity, robustness andsubstrate adhesion, (iii) a resist composition comprising the polymer asa base resin, which has a higher resolution and etching resistance thanconventional resist compositions, and (iv) a patterning process usingthe resist composition.

[0006] It has been found that novel ether compounds of formula (1) belowwhich are produced by the method to be described later can form polymershaving improved substrate adhesion, and that novel polymers obtainedtherefrom and having a weight average molecular weight of 1,000 to500,000 have improved reactivity, robustness or rigidity and substrateadhesion; that a resist composition comprising the polymer as the baseresin has a high resolution and etching resistance; and that this resistcomposition lends itself to precise micropatterning.

[0007] In a first aspect, the invention provides an ether compound ofthe following general formula (1).

[0008] Herein R¹ is hydrogen or a straight, branched or cyclic alkylgroup of 1 to 6 carbon atoms, R² is a straight, branched or cyclic alkylgroup of 1 to 6 carbon atoms, R³ is hydrogen or an acyl oralkoxycarbonyl group of 1 to 15 carbon atoms in which some or all of thehydrogen atoms on the constituent carbon atoms may be substituted withhalogen atoms, k is 0 or 1, m is an integer from 0 to 3, and n is aninteger from 3 to 6.

[0009] In a second aspect, the invention provides a polymer comprisingrecurring units of the following general formula (1-1) or (1-2) derivedfrom the ether compound of the above formula (1) and having a weightaverage molecular weight of 1,000 to 500,000.

[0010] Herein k, m, n, and R¹ to R³ are as defined above.

[0011] In one preferred embodiment, the polymer contains, in addition tothe recurring units of formula (1-1), recurring units of the followinggeneral formula (2-1).

[0012] Herein k is as defined above; R⁴ is hydrogen, methyl or CH₂CO₂R⁶;R⁵ is hydrogen, methyl or CO₂R⁶; R⁶ is a straight, branched or cyclicalkyl group of 1 to 15 carbon atoms; R⁷ is an acid labile group; R⁸ isselected from the class consisting of a halogen atom, a hydroxyl group,a straight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy groupof 1 to 15 carbon atoms, and a straight, branched or cyclicalkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbon atoms, inwhich some or all of the hydrogen atoms on constituent carbon atoms maybe substituted with halogen atoms; Z is a single bond or a straight,branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5 carbonatoms, in which at least one methylene may be substituted with oxygen toform a chain-like or cyclic ether or two hydrogen atoms on a commoncarbon may be substituted with oxygen to form a ketone; and p is 0, 1 or2.

[0013] In another preferred embodiment, the polymer contains, inaddition to the recurring units of formula (1-1), recurring units of thefollowing general formulae (2-1) and (3).

[0014] Herein Z, k, p and R⁴ to R⁸ are as defined above, and Y is anoxygen atom or NR⁹ wherein R⁹ is a straight, branched or cyclic alkylgroup of 1 to 6 carbon atoms.

[0015] In a further preferred embodiment, the polymer contains, inaddition to the recurring units of formula (1-1), recurring units of thefollowing general formula (4) alone or in combination with recurringunits of the following general formula (2-1), and recurring units of thefollowing general formula (3).

[0016] Herein Y, Z, k, p and R⁴ to R⁹ are as defined above.

[0017] In a still further preferred embodiment, the polymer contains, inaddition to the recurring units of formula (1-2), recurring units of thefollowing general formula (2-2).

[0018] Herein Z, k, p and R⁴ to R⁸ are as defined above.

[0019] In a third aspect, the invention provides a resist compositioncomprising the polymer defined above.

[0020] In a fourth aspect, the invention provides a process for forminga resist pattern comprising the steps of applying the resist compositiononto a substrate to form a coating; heat treating the coating and thenexposing it to high-energy radiation or electron beams through a photomask; and optionally heat treating the exposed coating and developing itwith a developer.

[0021] The ether compounds of formula (1) are highly polar due to theinclusion of a hydroxyl, acyloxy or alkoxycarbonyloxy group as well asan ether structure. The polymers comprising recurring units of formula(1-1) or (1-2) derived from the ether compounds thus exhibit improvedsubstrate adhesion. The polymers also have high rigidity since bridgedaliphatic rings are incorporated in the backbone. A carbon chain of anappropriate length introduced between the ether structure and the rigidbackbone serves to properly alleviate the rigidity which has beenexcessive in the prior art. Since the ether structure moiety is spacedapart from the backbone, it can act more positively as a polar group.These factors cooperate to develop a substrate adhesion force surpassingthe prior art compositions. Although low reactivity is left outstandingin the prior art, the carbon chain introduced allows the acid generatedto diffuse, thereby improving reactivity and as an accompanying benefit,achieving a reduction of line edge roughness. Therefore, a resistcomposition using the polymer as a base resin satisfies all theperformance factors of sensitivity, resolution and etch resistance andis very useful in forming micropatterns.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Ether

[0023] The ether compound of the invention has the following generalformula (1).

[0024] Herein R¹ is hydrogen or a straight, branched or cyclic alkylgroup of 1 to 6 carbon atoms. Exemplary alkyl groups include methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, and cyclohexyl. R² is astraight, branched or cyclic alkyl group of 1 to 6 carbon atoms,examples of which are the same as exemplified for R¹. R³ is hydrogen oran acyl or alkoxycarbonyl group of 1 to 15 carbon atoms in which some orall of the hydrogen atoms on the constituent carbon atoms may besubstituted with halogen atoms. Exemplary of R³ are formyl, acetyl,propionyl, pivaloyl, methoxycarbonyl, ethoxycarbonyl,tert-butoxycarbonyl, trifluoroacetyl, trichloroacetyl, and3,3,3-trifluoropropionyl. The letter k is 0 or 1, m is an integer from 0to 3, and n is an integer from 3 to 6.

[0025] Illustrative, non-limiting, examples of the ether compound offormula (1) are given below. In the formulae below and throughout thespecification, Ac is acetyl and t-Bu is tert-butyl.

[0026] The ether compound of the invention can be prepared according tothe following reaction scheme, but the invention is not limited thereto.

[0027] Herein, k, m, n, and R¹ to R³ are as defined above, X′ is ahalogen atom, and L is an eliminatable group such as hydroxyl, halogen,acyloxy, alkoxycarbonyloxy or p-nitrophenyloxy group.

[0028] Step A is to subject a carbonyl compound (b) to nucleophilicaddition reaction using a Grignard reagent prepared from a halogenatedether (a) and magnesium, thereby forming an alcohol (c). Grignardreaction is referred to as a typical example of nucleophilic additionreaction, but this step is not limited thereto. The reaction readilytakes place under well-known conditions although it is preferred to mixthe reactants, halogenated ether (a), carbonyl compound (b) andmagnesium in a solvent such as tetrahydrofuran or diethyl ether, whileheating or cooling the reaction solution if necessary.

[0029] Step B is to esterify the alcohol (c) into a corresponding acylor alkoxycarbonyl compound (d). The esterifying agents R³L used hereininclude carboxylic acids (where L=OH) such as formic acid, acid halides(where L=halogen) such as acetyl chloride, acetyl bromide and propionylchloride, acid anhydrides (where L=acyloxy or alkoxycarbonyloxy) such asacetic anhydride, trifluoroacetic anhydride, mixed acid anhydride offormic acid/acetic acid, and di-t-butyl dicarbonate, and activatedesters (where L an eliminatable group such as p-nitrophenyloxy) such asp-nitrophenyl acetate and p-nitrophenyl propionate. Except the casewhere the esterifying agent is carboxylic acid, it is desired to use abase such as triethylamine, pyridine and 4-dimethylaminopyridine. Thereaction readily takes place under well-known conditions although it ispreferred to mix the reactants, alcohol (c), esterifying agent R³L andoptionally, the base in a solventless system or in a solvent such astetrahydrofuran, diethyl ether, n-hexane or toluene, while heating orcooling the reaction solution if necessary.

[0030] Polymer

[0031] The polymers or high molecular weight compounds according to theinvention are characterized by comprising recurring units of thefollowing general formula (1-1) or (1-2) derived from the ether compoundof formula (1) and having a weight average molecular weight of 1,000 to500,000.

[0032] Herein k, m, n and R¹ to R ³ are as defined above.

[0033] More specifically, the polymers of the invention are divided intothe following four subgenuses of polymers.

[0034] Subgenus (I) includes polymers comprising, in addition to therecurring units of formula (1-1), recurring units of the followinggeneral formula (2-1).

[0035] Herein k is as defined above; R⁴ is hydrogen, methyl or CH₂CO₂R⁶;R⁵ is hydrogen, methyl or C₂O R⁶; R⁶ is a straight, branched or cyclicalkyl group of 1 to 15 carbon atoms; R⁷ is an acid labile group; R⁸ isselected from the class consisting of a halogen atom, a hydroxyl group,a straight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy groupof 1 to 15 carbon atoms, and a straight, branched or cyclicalkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbon atoms, inwhich some or all of the hydrogen atoms on constituent carbon atoms maybe substituted with halogen atoms; Z is a single bond or a straight,branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5 carbonatoms, in which at least one methylene may be substituted with oxygen toform a chain-like or cyclic ether or two hydrogen atoms on a commoncarbon may be substituted with oxygen to form a ketone; and p is 0, 1 or2.

[0036] Subgenus (II) includes polymers comprising, in addition to therecurring units of formula (1-1), recurring units of the followinggeneral formulae (2-1) and (3).

[0037] Herein Z, k, p and R⁴ to R⁸ are as defined above. Y is an oxygenatom or NR⁹ wherein R⁹ is a straight, branched or cyclic alkyl group of1 to 6 carbon atoms. Examples of R⁹ include methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

[0038] Subgenus (III) includes polymers comprising, in addition to therecurring units of formula (1-1), recurring units of the followinggeneral formula (4) alone or in combination with recurring units of thefollowing general formula (2-1), and recurring units of the followinggeneral formula (3).

[0039] Herein Y, Z, k, p and R⁴ to R⁹ are as defined above.

[0040] Subgenus (IV) includes polymers comprising, in addition to therecurring units of formula (1-2), recurring units of the followinggeneral formula (2-2).

[0041] Herein Z, k, p and R⁴ to R⁸ are as defined above.

[0042] More particularly, R⁴ is hydrogen, methyl or CH₂CO₂R⁶. R⁵ ishydrogen, methyl or CO₂R⁶. R⁶ stands for straight, branched or cyclicalkyl groups of 1 to 15 carbon atoms, such as, for example, methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl and butyladamantyl. R⁷ stands for acid labile groups tobe described later.

[0043] R⁸ is selected from among a halogen atom, a hydroxyl group, astraight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy groupof 1 to 15 carbon atoms, and a straight, branched or cyclicalkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbon atoms, inwhich some or all of the hydrogen atoms on constituent carbon atoms maybe substituted with halogen atoms. Exemplary of R⁸ are fluoro, chloro,bromo, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy,tert-butoxy, tert-amyloxy, n-pentoxy, n-hexyloxy, cyclopentyloxy,cyclohexyloxy, ethylcyclopentyloxy, butylcyclopentyloxy,ethylcyclohexyloxy, butylcyclohexyloxy, adamantyloxy, ethyladamantyloxy,butyladamantyloxy, formyloxy, acetoxy, ethylcarbonyloxy, pivaloyloxy,methoxycarbonyloxy, ethoxycarbonyloxy, tert-butoxycarbonyloxy,methanesulfonyloxy, ethanesulfonyloxy, n-butanesulfonyloxy,trifluoroacetoxy, trichloroacetoxy, 2,2,2-trifluoroethylcarbonyloxy,methoxymethoxy, 1-ethoxyethoxy, 1-ethoxypropoxy, 1-tert-butoxyethoxy,1-cyclohexyloxyethoxy, 2-tetrahydrofuranyloxy, and2-tetrahydropyranyloxy.

[0044] Z is a single bond or a straight, branched or cyclic (p+2)-valenthydrocarbon group of 1 to 5 carbon atoms, in which at least onemethylene may be substituted with oxygen to form a chain-like or cyclicether or two hydrogen atoms on a common carbon may be substituted withoxygen to form a ketone. In case of p=0, for example, exemplary Z groupsare methylene, ethylene, trimethylene, tetramethylene, pentamethylene,hexamethylene, 1,2-propanediyl, 1,3-butanediyl,1-oxo-2-oxapropane-1,3-diyl, 3-methyl-1-oxo-2-oxabutane-1,4-diyl. Incase of p≠0, exemplary Z groups are (p+2)-valent groups obtained byeliminating one or two hydrogen atoms from the above-exemplified groups.

[0045] The acid labile groups represented by R⁷ may be selected from avariety of such groups. Examples of the acid labile group are groups ofthe following general formulae (L1) to (L4), tertiary alkyl groups of 4to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilylgroups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms.

[0046] In these formulae and throughout the specification, the brokenline denotes a free valence bond. R^(L01) and R^(L02) are hydrogen orstraight, branched or cyclic alkyl groups of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms. Exemplary alkyl groups include methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, 2-ethylhexyl, and n-octyl. R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, which may contain a hetero atom such as oxygen, examples of whichinclude unsubstituted straight, branched or cyclic alkyl groups andstraight, branched or cyclic alkyl groups in which some hydrogen atomsare replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like.Illustrative examples are the substituted alkyl groups shown below.

[0047] A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02)and R^(L03) may form a ring. Each of R^(L01), R^(L02) and R^(L03) is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms when they form a ring.

[0048] R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms,preferably 4 to 15 carbon atoms, a trialkylsilyl group in which eachalkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkylsilylgroups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl.Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl,and 5-methyl-2-oxooxolan-5-yl. Letter x is an integer of 0 to 6.

[0049] R^(L05) is a monovalent hydrocarbon group of 1 to 8 carbon atomswhich may contain a hetero atom or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms. Examples of the monovalent hydrocarbongroup which may contain a hetero atom include straight, branched orcyclic alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, andcyclohexyl, and substituted groups in which some hydrogen atoms on theforegoing groups are substituted with hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups. Exemplary aryl groups are phenyl, methylphenyl,naphthyl, anthryl, phenanthryl, and pyrenyl. Letter y is equal to 0 or1, z is equal to 0, 1, 2 or 3, and 2y+z is equal to 2 or 3.

[0050] R^(L06) is a monovalent hydrocarbon group of 1 to 8 carbon atomswhich may contain a hetero atom or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms. Examples of these groups are the same asexemplified for R^(L05).

[0051] R^(L07) to R^(L16) independently represent hydrogen or monovalenthydrocarbon groups of 1 to 15 carbon atoms which may contain a heteroatom. Exemplary hydrocarbon groups are straight, branched or cyclicalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl,and substituted ones of these groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups.Alternatively, R^(L07) to R^(L16), taken together, form a ring (forexample, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09), R^(L08) andR^(L10) R^(L09) and R^(L10) , R^(L11) and R^(L12), R^(L13) and R^(L14),or a similar pair form a ring). Each of R^(L07) to R^(L16) represents adivalent C₁-C₁₅ hydrocarbon group which may contain a hetero atom, whenthey form a ring, examples of which are the ones exemplified above forthe monovalent hydrocarbon groups, with one hydrogen atom beingeliminated. Two of R^(L07) to R^(L16) which are attached to adjoiningcarbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), R^(L09) and R^(L15), R^(L13) and R^(L15),or a similar pair) may bond together directly to form a double bond.

[0052] Of the acid labile groups of formula (L1), the straight andbranched ones are exemplified by the following groups.

[0053] Of the acid labile groups of formula (L1), the cyclic ones are,for example, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

[0054] Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxy-carbonylmethyl,1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonyl-methyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

[0055] Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclo-pentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

[0056] The acid labile groups of formula (L4) are exemplified by thefollowing groups.

[0057] Examples of the tertiary alkyl groups of 4 to 20 carbon atoms,trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms,and oxoalkyl groups of 4 to 20 carbon atoms are as exemplified forR^(L04).

[0058] Illustrative, non-limiting, examples of the recurring units offormula (1-1) are given below.

[0059] Illustrative, non-limiting, examples of the recurring units offormula (1-2) are given below.

[0060] Illustrative, non-limiting, examples of the recurring units offormula (2-1) are given below.

[0061] Illustrative, non-limiting, examples of the recurring units offormula (2-2) are given below.

[0062] Illustrative, non-limiting, examples of the recurring units offormula (4) are given below.

[0063] If desired, the polymers of the invention may further containrecurring units of one or more types selected from units of thefollowing general formulae (M1) to (M8-2).

[0064] Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³, R⁰⁰² is hydrogen,methyl or CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of1 to 15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon groupof 1 to 15 carbon atoms having a carboxyl or hydroxyl group. At leastone of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15carbon atoms having a carboxyl or hydroxyl group while the remaining R'sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R's are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbonatoms containing a —CO₂— partial structure. At least one of R⁰¹⁰ to R⁰¹³is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a—CO₂— partial structure, while the remaining R′s are independentlyhydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbonatoms. R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event,at least one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR's are independently single bonds or straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms. R⁰¹⁴ is a polycyclichydrocarbon group having 7 to 15 carbon atoms or an alkyl groupcontaining a polycyclic hydrocarbon group. R⁰¹⁵ is an acid labile group.X is CH₂ or an oxygen atom. Letter k is equal to 0 or 1.

[0065] More illustratively, R⁰⁰³ is a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms, for example, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl,ethylcyclohexyl, butyl-cyclohexyl, adamantyl, ethyladamantyl, andbutyladamantyl.

[0066] R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1 to 15carbon atoms having a carboxyl or hydroxyl group, for example,carboxyethyl, carboxybutyl, carboxycyclopentyl, carboxycyclohexyl,carboxynorbornyl, carboxyadamantyl, hydroxyethyl, hydroxybutyl,hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl, andhydroxyadamantyl.

[0067] At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbongroup of 1 to 15 carbon atoms having a carboxyl or hydroxyl group whilethe remaining R′s independently represent hydrogen or a straight,branched or cyclic alkyl group of 1 to 15 carbon atoms. Examples of thecarboxyl or hydroxyl-bearing monovalent hydrocarbon group of 1 to 15carbon atoms include carboxy, carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl, andhydroxyadamantyloxycarbonyl. Examples of the straight, branched orcyclic alkyl group of 1 to 15 carbon atoms are the same as exemplifiedfor R⁰⁰³.

[0068] Alternatively, R⁰⁰⁵ to R⁰⁰⁸, taken together, may form a ring, andin that event, at least one of R⁰⁰⁵ to R⁰⁰⁸ is a divalent hydrocarbongroup of 1 to 15 carbon atoms having a carboxyl or hydroxyl group, whilethe remaining R′s are independently single bonds or straight, branchedor cyclic alkylene groups of 1 to 15 carbon atoms. Examples of thecarboxyl or hydroxyl-bearing divalent hydrocarbon group of 1 to 15carbon atoms include the groups exemplified as the carboxyl orhydroxyl-bearing monovalent hydrocarbon group, with one hydrogen atomeliminated therefrom. Examples of the straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms include the groups exemplifiedfor R⁰⁰³, with one hydrogen atom eliminated therefrom.

[0069] R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbon atomscontaining a —CO₂— partial structure, for example, 2-oxooxolan-3-yl,4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl,2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

[0070] At least one of R⁰¹⁰ to R⁰¹³ is a monovalent hydrocarbon group of2 to 15 carbon atoms containing a —CO₂— partial structure, while theremaining R′s are independently hydrogen or straight, branched or cyclicalkyl groups of 1 to 15 carbon atoms. Examples of the monovalenthydrocarbon group of 2 to 15 carbon atoms containing a —CO₂— partialstructure include 2-oxooxolan-3-yloxycarbonyl,4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic alkyl groups of 1 to 15 carbon atoms are the same asexemplified for R⁰⁰³

[0071] R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event,at least one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR′s are independently single bonds or straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms. Examples of the divalenthydrocarbon group of 1 to 15 carbon atoms containing a —CO₂— partialstructure include 1-oxo-2-oxapropane-1,3-diyl,1,3-dioxo-2-oxapropane-1,3-diyl, 1-oxo-2-oxabutane-1,4-diyl, and1,3-dioxo-2-oxabutane-1,4-diyl, as well as the groups exemplified as themonovalent hydrocarbon group containing a —CO₂— partial structure, withone hydrogen atom eliminated therefrom. Examples of the straight,branched or cyclic alkylene groups of 1 to 15 carbon atoms include thegroups exemplified for R⁰⁰³, with one hydrogen atom eliminatedtherefrom.

[0072] R⁰¹⁴ is a polycyclic hydrocarbon group having 7 to 15 carbonatoms or an alkyl group containing a polycyclic hydrocarbon group, forexample, norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, ethyladamantyl, butyladamantyl, norbornylmethyl, andadamantylmethyl.

[0073] R⁰¹⁵ is an acid labile group, examples of which are the same asdescribed above. X is CH₂ or an oxygen atom. Letter k is equal to 0 or1.

[0074] The recurring units of formulae (M1) to (M8-2) are effective forimparting such desired properties as developer affinity, substrateadhesion and etching resistance to a resist composition based on apolymer comprising these recurring units. By adjusting the content ofthese recurring units, the performance of the resist composition can befinely adjusted.

[0075] The polymers of the invention have a weight average molecularweight of about 1,000 to 500,000, preferably about 3,000 to 100,000.Outside the range, the etching resistance may become extremely low andthe resolution may become low because a substantial difference in rateof dissolution before and after exposure is lost.

[0076] The polymer of the invention can be prepared throughcopolymerization reaction using a compound of the following generalformula (1a) as a first monomer, one, two or three members selected fromcompounds of the following general formulae (2a) to (4a) as second tofourth monomers, and optionally, one or more members selected fromcompounds of the following general formulae (M1a) to (M8a) as subsequentmonomers.

[0077] Herein, Y, Z, k, p, m, n, R¹ to R⁹ are as defined above.

[0078] Herein, k, R⁰⁰¹ to R⁰¹⁵, and X are as defined above.

[0079] By properly adjusting the proportion of the respective monomersused in the copolymerization reaction, the polymer can be tailored sothat it may exert the preferred performance when blended in resistcompositions.

[0080] In addition to (i) the monomer of formula (1a), (ii) the monomeror monomers of formulas (2a) to (4a), and (iii) the monomer or monomersof formulae (M1a) to (M8a), the polymer of the invention may havecopolymerized therewith (iv) another monomer having a carbon-to-carbondouble bond other than (i) to (iii). Examples of the additional monomer(iv) include substituted acrylic acid esters such as methylmethacrylate, methyl crotonate, dimethyl maleate, and dimethylitaconate, unsaturated carboxylic acids such as maleic acid, fumaricacid and itaconic acid, substituted or unsubstituted norbornenes such asnorbornene and methyl norbornene-5-carboxylate, and unsaturated acidanhydrides such as itaconic anhydride.

[0081] In the polymers of the invention, the preferred proportion ofrecurring units based on the respective monomers is in the followingrange (in mol %), though not limited thereto.

[0082] (I) When the polymer is comprised of recurring units of formula(1-1) and recurring units of formula (2-1), it contains

[0083] (i) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70%of recurring units of formula (1-1) based on the monomer of formula(1a),

[0084] (ii) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70%of recurring units of formula (2-1) based on the monomer of formula(2a),

[0085] (iii) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30%of recurring units of formula (M5-1) to (M8-1) based on the monomers offormula (M5a) to (M8a), and

[0086] (iv) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30%of recurring units based on another monomer.

[0087] (II) When the polymer is comprised of recurring units of formula(1-1), recurring units of formula (2-1) and recurring units of formula(3), it contains

[0088] (i) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40%of recurring units of formula (1-1) based on the monomer of formula(1a),

[0089] (ii) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40%of recurring units of formula (2-1) based on the monomer of formula(2a),

[0090] (iii) 50% of recurring units of formula (3) based on the monomerof formula (3a),

[0091] (iv) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15%of recurring units of formula (M5-1) to (M8-1) based on the monomers offormula (M5a) to (M8a), and

[0092] (v) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15%of recurring units based on another monomer.

[0093] (III) When the polymer is comprised of recurring units of formula(1-1), recurring units of formula (4) alone or in combination withrecurring units of formula (2-1), and recurring units of formula (3), itcontains

[0094] (i) 1 to 49%, preferably 3 to 45%, and more preferably 5 to 40%of recurring units of formula (1-1) based on the monomer of formula(1a),

[0095] (ii) 0 to 40%, preferably 0 to 35%, and more preferably 0 to 30%of recurring units of formula (2-1) based on the monomer of formula(2a),

[0096] (iii) 1 to 80%, preferably 1 to 70%, and more preferably 1 to 50%of recurring units of formula (4) based on the monomer of formula (4a),

[0097] (iv) 1 to 49%, preferably 5 to 45%, and more preferably 10 to 40%of recurring units of formula (3) based on the monomer of formula (3a),

[0098] (v) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15%of recurring units of formula (M1a) to (M8-1) based on the monomers offormula (M1a) to (M8a), and

[0099] (vi) 0 to 25%, preferably 0 to 20%, and more preferably 0 to 15%of recurring units based on another monomer.

[0100] (IV) When the polymer is comprised of recurring units of formula(1-2) and recurring units of formula (2-2), it contains

[0101] (i) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70%of recurring units of formula (1-2) based on the monomer of formula(1a),

[0102] (ii) 1 to 90%, preferably 5 to 80%, and more preferably 10 to 70%of recurring units of formula (2-2) based on the monomer of formula(2a),

[0103] (iii) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30%of recurring units of formula (M5-2) to (M8-2) based on the monomers offormula (M5a) to (M8a), and

[0104] (iv) 0 to 50%, preferably 0 to 40%, and more preferably 0 to 30%of recurring units based on another monomer.

[0105] A variety of copolymerization reaction methods may be used forthe preparation of the polymer according to the invention. The preferredpolymerization reaction is radical polymerization, anionicpolymerization or coordination polymerization.

[0106] For radical polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as benzene, etherssuch as tetrahydrofuran, alcohols such as ethanol, and ketones such asmethyl isobutyl ketone, (b) a polymerization initiator selected from azocompounds such as 2,2′-azobisisobutyronitrile and peroxides such asbenzoyl peroxide and lauroyl peroxide, (c) a temperature of about 0° C.to about 100° C., and (d) a time of about ½ hour to about 48 hours.Reaction conditions outside the described range may be employed ifdesired.

[0107] For anionic polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as benzene, etherssuch as tetrahydrofuran, and liquid ammonia, (b) a polymerizationinitiator selected from metals such as sodium and potassium, alkylmetals such as n-butyllithium and sec-butyllithium, ketyl, and Grignardreagents, (c) a temperature of about −78° C. to about 0° C., (d) a timeof about ½ hour to about 48 hours, and (e) a stopper selected from amongproton-donative compounds such as methanol, halides such as methyliodide, and electrophilic compounds. Reaction conditions outside thedescribed range may be employed if desired.

[0108] For coordination polymerization, preferred reaction conditionsinclude (a) a solvent selected from among hydrocarbons such as n-heptaneand toluene, (b) a catalyst selected from Ziegler-Natta catalystscomprising a transition metal (e.g., titanium) and alkylaluminum,Phillips catalysts of metal oxides having chromium or nickel compoundscarried thereon, and olefin-metathesis mixed catalysts as typified bytungsten and rhenium mixed catalysts, (c) a temperature of about 0° C.to about 100° C., and (d) a time of about ½ hour to about 48 hours.Reaction conditions outside the described range may be employed ifdesired.

[0109] Resist Composition

[0110] Since the polymer of the invention is useful as the base resin ofa resist composition, the other aspect of the invention provides aresist composition, especially a chemically amplified positive resistcomposition, comprising the polymer. Typically, the resist compositioncontains the polymer, a photoacid generator, and an organic solvent, andother optional components.

[0111] Photoacid Generator

[0112] The photoacid generator is a compound capable of generating anacid upon exposure to high energy radiation or electron beams andincludes the following:

[0113] (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),

[0114] (ii) diazomethane derivatives of the formula (P2),

[0115] (iii) glyoxime derivatives of the formula (P3),

[0116] (iv) bissulfone derivatives of the formula (P4),

[0117] (v) sulfonic acid esters of N-hydroxyimide compounds of theformula (P5),

[0118] (vi) β-ketosulfonic acid derivatives,

[0119] (vii) disulfone derivatives,

[0120] (viii) nitrobenzylsulfonate derivatives, and

[0121] (ix) sulfonate derivatives.

[0122] These photoacid generators are described in detail.

[0123] (i) Onium salts of formula (P1a-1), (P1a-2) or (P1b):

[0124] Herein, R¹⁰¹, R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

[0125] R^(101a), R^(101b), and R^(101c) may be the same or different andare illustrated below. Exemplary alkyl groups include methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl,heptyl, octyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K- include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

[0126] Herein, R^(102a) and R^(102b) independently represent straight,branched or cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ representsa straight, branched or cyclic alkylene groups of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K³¹ is a non-nucleophilic counter ion.

[0127] Illustrative of the groups represented by R^(102a) and R^(102b)are methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

[0128] (ii) Diazomethane derivatives of formula (P2)

[0129] Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms.

[0130] Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkylgroups include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methyl-phenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

[0131] (iii) Glyoxime derivatives of formula (P3)

[0132] Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight,branched or cyclic alkyl or halogenated alkyl groups of 1 to 12 carbonatoms, aryl or halogenated aryl groups of 6 to 20 carbon atoms, oraralkyl groups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, takentogether, may form a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branchedalkylene groups of 1 to 6 carbon atoms when they form a ring.

[0133] Illustrative examples of the alkyl, halogenated alkyl, aryl,halogenated aryl, and aralkyl groups represented by R¹⁰⁷ , R¹⁰⁸, andR¹⁰⁹ are the same as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of thealkylene groups represented by R¹⁰⁸ and R¹⁰⁹ include methylene,ethylene, propylene, butylene, and hexylene.

[0134] (iv) Bissulfone derivatives of formula (P4)

[0135] Herein, R^(101a) and R^(101b) are as defined above.

[0136] (v) Sulfonic acid esters of N-hydroxyimide compounds of formula(P5)

[0137] Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms,alkylene group of 1 to 6 carbon atoms, or alkenylene group of 2 to 6carbon atoms wherein some or all of the hydrogen atoms may be replacedby straight or branched alkyl or alkoxy groups of 1 to 4 carbon atoms,nitro, acetyl, or phenyl groups. R¹¹¹ is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl ornaphthyl group wherein some or all of the hydrogen atoms may be replacedby alkyl or alkoxy groups of 1 to 4 carbon atoms, phenyl groups (whichmay have substituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms,nitro, or acetyl group), hetero-aromatic groups of 3 to 5 carbon atoms,or chlorine or fluorine atoms.

[0138] Of the groups represented by R¹¹⁰, exemplary arylene groupsinclude 1,2-phenylene and 1,8-naphthylene; exemplary alkylene groupsinclude methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene,1-phenyl-1,2-ethylene, and norbornane-2,3-diyl; and exemplary alkenylenegroups include 1,2-vinylene, 1-phenyl-1,2-vinylene, and5-norbornene-2,3-diyl. Of the groups represented by R¹¹¹, exemplaryalkyl groups are as exemplified for R^(101a) to R^(101c); exemplaryalkenyl groups include vinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl,isoprenyl, 1-pentenyl, 3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl,3-hexenyl, 5-hexenyl, 1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl;and exemplary alkoxyalkyl groups include methoxymethyl, ethoxymethyl,propoxymethyl, butoxymethyl, pentyloxymethyl, hexyloxymethyl,heptyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl,pentyloxyethyl, hexyloxyethyl, methoxypropyl, ethoxypropyl,propoxypropyl, butoxypropyl, methoxybutyl, ethoxybutyl, propoxybutyl,methoxypentyl, ethoxypentyl, methoxyhexyl, and methoxyheptyl.

[0139] Of the substituents on these groups, the alkyl groups of 1 to 4carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyland tert-butyl; the alkoxy groups of 1 to 4 carbon atoms includemethoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, andtert-butoxy; the phenyl groups which may have substituted thereon analkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group includephenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl;the hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl andfuryl.

[0140] Illustrative examples of the photoacid generator include:

[0141] onium salts such as diphenyliodonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)phenyliodoniump-toluenesulfonate, triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfoniumbutanesulfonate, trimethylsulfonium trifluoromethanesulfonate,trimethylsulfonium p-toluenesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,dimethylphenylsulfonium trifluoromethanesulfonate,dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfoniumtrifluoromethanesulfonate, dicyclohexylphenylsulfoniump-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,ethylenebis[methyl(2-oxocyclopentyl)sulfoniumtrifluoromethanesulfonate], and1,2′-naphthylcarbonylmethyl-tetrahydrothiophenium triflate;

[0142] diazomethane derivatives such asbis(benzene-sulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(xylenesulfonyl)diazomethane, bis(cyclohexyl-sulfonyl)diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutyl-sulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropyl-sulfonyl)diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane,bis(isoamyl-sulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane,bis(tert-amylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

[0143] glyoxime derivatives such asbis-O-(p-toluene-sulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butane--sulfonyl)-α-dicyclohexylglyoxime,bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(tert-butanesulfonyl)-α-dimethyl-glyoxime,bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluoro-benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime, andbis-O-(camphorsulfonyl)-α-dimethylglyoxime;

[0144] bissulfone derivatives such as bisnaphthylsulfonylmethane,bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane,bisethylsulfonylmethane, bispropylsulfonylmethane,bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, andbisbenzenesulfonylmethane;

[0145] β-ketosulfone derivatives such as2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

[0146] disulfone derivatives such as diphenyl disulfone and dicyclohexyldisulfone;

[0147] nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzylp-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

[0148] sulfonic acid ester derivatives such as1,2,3-tris-(methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; and

[0149] sulfonic acid esters of N-hydroxyimides such asN-hydroxysuccinimide methanesulfonate, N-hydroxysuccinimidetrifluoromethanesulfonate, N-hydroxysuccinimide ethanesulfonate,N-hydroxysuccinimide 1-propanesulfonate, N-hydroxysuccinimide2-propanesulfonate, N-hydroxysuccinimide 1-pentanesulfonate,N-hydroxysuccinimide 1-octanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxysuccinimide p-methoxybenzenesulfonate,N-hydroxysuccinimide 2-chloroethanesulfonate, N-hydroxysuccinimidebenzenesulfonate, N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate,N-hydroxymaleimide methanesulfonate, N-hydroxymaleimide ethanesulfonate,N-hydroxy-2-phenylmaleimide methanesulfonate, N-hydroxyglutarimidemethanesulfonate, N-hydroxyglutarimide benzenesulfonate,N-hydroxy-phthalimide methanesulfonate, N-hydroxyphthalimidebenzene-sulfonate, N-hydroxyphthalimide trifluoromethanesulfonate,N-hydroxyphthalimide p-toluenesulfonate, N-hydroxynaphthalimidemethanesulfonate, N-hydroxynaphthalimide benzene-sulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,N-hydroxy-5-norbornene-2,3-dicarboxyimide trifluoromethanesulfonate, andN-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

[0150] Preferred among these photoacid generators are onium salts suchas triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoro-methanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoro-methanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoro-methanesulfonate,and 1,2′-naphthylcarbonylmethyltetrahydro-thiophenium triflate;diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluene-sulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutyl-sulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropyl-sulfonyl)diazomethane,and bis(tert-butylsulfonyl)diazo-methane; glyoxime derivatives such asbis-O-(p-toluene-sulfonyl)-α-dimethylglyoxime andbis-O-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives suchas bisnaphthylsulfonylmethane; and sulfonic acid esters ofN-hydroxyimide compounds such as N-hydroxysuccinimide methane-sulfonate,N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentane-sulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, andN-hydroxy-naphthalimide benzenesulfonate.

[0151] These photoacid generators may be used singly or in combinationsof two or more thereof. Onium salts are effective for improvingrectangularity, while diazomethane derivatives and glyoxime derivativesare effective for reducing standing waves. The combination of an oniumsalt with a diazomethane or a glyoxime derivative allows for fineadjustment of the profile.

[0152] The photoacid generator is added in an amount of 0.1 to 15 parts,and especially 0.5 to 8 parts by weight, per 100 parts by weight of thebase resin (all parts are by weight, hereinafter). Less than 0.1 part ofthe photoacid generator would provide a poor sensitivity whereas morethan 15 parts of the photoacid generator would adversely affecttransparency and resolution.

[0153] Organic Solvent

[0154] The organic solvent used herein may be any organic solvent inwhich the base resin, photoacid generator, and other components aresoluble. Illustrative, non-limiting, examples of the organic solventinclude ketones such as cyclohexanone and methyl-2-n-amylketone;alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol,1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propyleneglycol monomethyl ether, ethylene glycol monomethyl ether, propyleneglycol monoethyl ether, ethylene glycol monoethyl ether, propyleneglycol dimethyl ether, and diethylene glycol dimethyl ether; and esterssuch as propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate,methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butylacetate, tert-butyl propionate, and propylene glycol mono-tert-butylether acetate. These solvents may be used alone or in combinations oftwo or more thereof. Of the above organic solvents, it is recommended touse diethylene glycol dimethyl ether and 1-ethoxy-2-propanol because thephotoacid generator is most soluble therein, propylene glycol monomethylether acetate because it is a safe solvent, or a mixture thereof.

[0155] An appropriate amount of the organic solvent used is about 200 to1,000 parts, especially about 400 to 800 parts by weight per 100 partsby weight of the base resin.

[0156] Other Polymer

[0157] To the resist composition of the invention, another polymer otherthan the inventive polymer comprising recurring units of formula (1-1)or (1-2) may also be added. The other polymers that can be added to theresist composition are, for example, those polymers comprising units ofthe following formula (R1) and/or (R2) and having a weight averagemolecular weight of about 1,000 to about 500,000, especially about 5,000to about 100,000 although the other polymers are not limited thereto.

[0158] Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen,methyl or CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of1 to 15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon groupof 1 to 15 carbon atoms having a carboxyl or hydroxyl group. At leastone of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15carbon atoms having a carboxyl or hydroxyl group while the remaining R′sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R′s are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbonatoms containing a —CO₂— partial structure. At least one of R⁰¹⁰ to R⁰¹³is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a—CO₂— partial structure, while the remaining R′s are independentlyhydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbonatoms. R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event,at least one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR′s are independently single bonds or straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms. R⁰¹⁴ is a polycyclichydrocarbon group having 7 to 15 carbon atoms or an alkyl groupcontaining a polycyclic hydrocarbon group. R⁰¹⁵ is an acid labile group.R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms. X is CH₂ or an oxygen atom. Y is an oxygenatom or NR⁰¹⁸ wherein R⁰¹⁸ is a straight, branched or cyclic alkyl groupof 1 to 6 carbon atoms. Letter k is equal to 0 or 1; a1′, a2′, a3′, b1′,b2′, b3′, c1′, c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 toless than 1, satisfyinga1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′, h′, i′,and j′ are numbers from 0 to less than 1, satisfying f′+g′+h′+i′+j′=1.

[0159] Exemplary groups of these R′s are as exemplified above.

[0160] The inventive polymer (comprising recurring units of formula(1-1) or (1-2)) and the other polymer are preferably blended in a weightratio from 100:0 to 10:90, more preferably from 100:0 to 20:80. If theblend ratio of the inventive polymer is below this range, the resistcomposition would become poor in some of the desired properties. Theproperties of the resist composition can be adjusted by properlychanging the blend ratio of the inventive polymer.

[0161] The other polymer is not limited to one type and a mixture of twoor more other polymers may be added. The use of plural polymers allowsfor easy adjustment of resist properties.

[0162] Dissolution Regulator

[0163] To the resist composition, a dissolution regulator may be added.The dissolution regulator is a compound having on the molecule at leasttwo phenolic hydroxyl groups, in which an average of from 0 to 100 mol %of all the hydrogen atoms on the phenolic hydroxyl groups are replacedwith acid labile groups or a compound having on the molecule at leastone carboxyl group, in which an average of 50 to 100 mol % of all thehydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having an average molecular weight within arange of 100 to 1,000, and preferably 150 to 800.

[0164] The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

[0165] Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

[0166] In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straightor branched alkyl or alkenyl of 1 to 8 carbon atoms; R²⁰³ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or—(R²⁰⁷)_(h)—COOH; R²⁰⁴ is —(CH₂)_(i) (where i=2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R²⁰⁵ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straightor branched alkylene of 1 to 10 carbon atoms; R²⁰⁸ is hydrogen orhydroxyl; the letter j is an integer from 0 to 5; u and h are each 0 or1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t =8,s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has atleast one hydroxyl group; and α is a number such that the compounds offormula (D8) or (D9) have a molecular weight of from 100 to 1,000.

[0167] In the above formulas, suitable examples of R²⁰¹ and R²⁰² includehydrogen, methyl, ethyl, butyl, propyl, ethynyl, and cyclohexyl;suitable examples of R²⁰³ include the same groups as for R²⁰¹ and R²⁰²,as well as —COOH and —CH₂COOH; suitable examples of R²⁰⁴ includeethylene, phenylene, carbonyl, sulfonyl, oxygen, and sulfur; suitableexamples of R²⁰⁵ include methylene as well as the same groups as forR²⁰⁴; and suitable examples of R²⁰⁶ include hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, and hydroxyl-substituted phenyl ornaphthyl.

[0168] Exemplary acid labile groups on the dissolution regulator includea variety of such groups, and typically groups of the following generalformulae (L1) to (L4), tertiary alkyl groups of 4 to 20 carbon atoms,trialkylsilyl groups in which each of the alkyls has 1 to 6 carbonatoms, and oxoalkyl groups of 4 to 20 carbon atoms.

[0169] In these formulas, R^(L01) and R^(L02) are each hydrogen or astraight, branched or cyclic alkyl having 1 to 18 carbon atoms; andR^(L03) is a monovalent hydrocarbon group of 1 to 18 carbon atoms whichmay contain a heteroatom (e.g., oxygen). A pair of R^(L01) and R^(L02),a pair of R^(L01) and R^(L03) or a pair of R^(L02) and R^(L03) maytogether form a ring, with the proviso that R^(L01), R^(L02), andR^(L03) are each a straight or branched alkylene of 1 to 18 carbon atomswhen they form a ring. R^(L04) is a tertiary alkyl group of 4 to 20carbon atoms, a trialkysilyl group in which each of the alkyls has 1 to6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or a group ofthe formula (L1). R^(L05) is a monovalent hydrocarbon groups of 1 to 8carbon atoms which may contain a hetero atom or a substituted orunsubstituted aryl group of 6 to 20 carbon atoms. R^(L06) is amonovalent hydrocarbon groups of 1 to 8 carbon atoms which may contain ahetero atom or a substituted or unsubstituted aryl group of 6 to 20carbon atoms. R^(L07) to R^(L06) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms which may containa hetero atom. Alternatively, R^(L07) to R^(L16), taken together, mayform a ring. Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group which may contain a hetero atom, when they form aring. Two of R^(L07) to R^(L16) which are attached to adjoining carbonatoms may bond together directly to form a double bond. Letter x is aninteger of 0 to 6. Letter y is equal to 0 or 1, z is equal to 0, 1, 2 or3, and 2y+z is equal to 2 or 3. Illustrative examples of these groupsare as previously exemplified.

[0170] The dissolution regulator may be formulated in an amount of 0 to50 parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts,per 100 parts of the base resin, and may be used singly or as a mixtureof two or more thereof. The use of more than 50 parts would lead toslimming of the patterned film, and thus a decline in resolution.

[0171] The dissolution regulator can be synthesized by introducing acidlabile groups into a compound having phenolic hydroxyl or carboxylgroups in accordance with an organic chemical formulation.

[0172] Basic Compound

[0173] In the resist composition of the invention, a basic compound maybe blended. A suitable basic compound used herein is a compound capableof suppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

[0174] Examples of basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, carboxyl group-bearing nitrogenous compounds, sulfonylgroup-bearing nitrogenous compounds, hydroxyl group-bearing nitrogenouscompounds, hydroxyphenyl group-bearing nitrogenous compounds, alcoholicnitrogenous compounds, amide derivatives, and imide derivatives.

[0175] Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylene-diamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethyl-methylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

[0176] Examples of suitable mixed amines include dimethyl-ethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methyl-pyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridone, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

[0177] Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable sulfonyl group-bearing nitrogenous compounds include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenylgroup-bearing nitrogenous compounds, and alcoholic nitrogenous compoundsinclude 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,triisopropanolamine, 2,2′-iminodiethanol, 2-amino-ethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

[0178] In addition, basic compounds of the following general formula(B1) may also be included alone or in admixture.

N(X)_(n)(Y)_(3−n)  (B1)

[0179] In the formula, n is equal to 1, 2 or 3; side chain Y isindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 20 carbon atoms which may contain a hydroxyl group or ether; andside chain X is independently selected from groups of the followinggeneral formulas (X1) to (X3), and two or three X′s may bond together toform a ring.

[0180] In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straightor branched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a singlebond or a straight, branched or cyclic alkyl group of 1 to 20 carbonatoms which may contain one or more hydroxyl groups, ether groups, estergroups or lactone rings.

[0181] Illustrative examples of the compounds of formula (B1) includetris(2-methoxymethoxyethyl)amine, tris{2-(methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}-amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxy-carbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonyl-ethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl) ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-((2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxy -carbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxy-ethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonyl-methyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

[0182] The basic compound is preferably formulated in an amount of 0.001to 10 parts, and especially 0.01 to 1 part, per part of the photoacidgenerator. Less than 0.001 part of the basic compound may fail toachieve the desired effects thereof, while the use of more than 10 partswould result in too low a sensitivity and resolution.

[0183] Other Components

[0184] In the resist composition, a compound bearing a ≡C—COOH group ina molecule may be blended. Exemplary, non-limiting compounds bearing a≡—C—COOH group include one or more compounds selected from Groups I andII below. Including this compound improves the PED stability of theresist and ameliorates edge roughness on nitride film substrates.

[0185] Group I

[0186] Compounds in which some or all of the hydrogen atoms on thephenolic hydroxyl groups of the compounds of general formulas (A1) to(A10) below have been replaced with —R⁴⁰¹—COOH (wherein R⁴⁰¹ is astraight or branched alkylene of 1 to 10 carbon atoms), and in which themolar ratio C/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups(D) in the molecule is from 0.1 to 1.0.

[0187] In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ areeach hydrogen or a straight or branched alkyl or alkenyl of 1 to 8carbon atoms; R⁴⁰⁴ is hydrogen, a straight or branched alkyl or alkenylof 1 to 8 carbon atoms, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogenor —R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)₁— (wherein i is 2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R⁴⁰⁶ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁷is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straightor branched alkylene of 1 to 10 carbon atoms; R⁴¹⁰ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or a—R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched alkylene of 1 to 10carbon atoms; the letter j is an integer from 0 to 5; u and h are each 0or 1; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfys1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenylskeleton has at least one hydroxyl group; κ is a number such that thecompound of formula (A6) may have a weight average molecular weight of1,000 to 5,000; and λ is a number such that the compound of formula (A7)may have a weight average molecular weight of 1,000 to 10,000.

[0188] Group II

[0189] Compounds of general formulas (A11) to (A15) below.

[0190] In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above;R⁴¹² is hydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0,t5≧0, and s5+t5=5; and h′ is equal to 0 or 1.

[0191] Illustrative, non-limiting examples of the compound bearing a≡—C—COOH group include compounds of the general formulas AI-1 to AI-14and AII-1 to AII-10 below.

[0192] In the above formulas, R″ is hydrogen or a CH₂COOH group suchthat the CH₂COOH group accounts for 10 to 100 mol % of R″ in eachcompound, a and K are as defined above.

[0193] The compound bearing a ≡C—COOH group within the molecule may beused singly or as combinations of two or more thereof.

[0194] The compound bearing a ≡C—COOH group within the molecule is addedin an amount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, further preferably 0.1 to 2 parts, per 100parts of the base resin. More than 5 parts of the compound can reducethe resolution of the resist composition.

[0195] The resist composition of the invention may additionally includean acetylene alcohol derivative for the purpose of enhancing the shelfstability. Preferred acetylene alcohol derivatives are those having thegeneral formula (S1) or (S2) below.

[0196] In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are eachhydrogen or a straight, branched, or cyclic alkyl of 1 to 8 carbonatoms; and X and Y are each 0 or a positive number, satisfying 0≦X≦30,0≦Y≦30, and 0≦X+Y≦40.

[0197] Preferable examples of the acetylene alcohol derivative includeSurfynol 61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H,Surfynol 104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, andSurfynol 485 from Air Products and Chemicals Inc., and Surfynol E1004from Nisshin Chemical Industry K.K.

[0198] The acetylene alcohol derivative is preferably added in an amountof 0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, per100% by weight of the resist composition. Less than 0.01% by weightwould be ineffective for improving coating characteristics and shelfstability, whereas more than 2% by weight would result in a resisthaving a low resolution.

[0199] The resist composition of the invention may include optionalingredients, for example, a surfactant which is commonly used forimproving the coating characteristics. Optional ingredients may be addedin conventional amounts so long as this does not compromise the objectsof the invention.

[0200] Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Florade FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141 and S-145 from Asahi Glass Co.,Ltd., Unidyne DS-401, DS-403 and DS-451 from Daikin Industry Co., Ltd.,Megaface F-8151 from Dai-Nippon Ink & Chemicals, Inc., and X-70-092 andX-70-093 from Shin-Etsu Chemical Co., Ltd. Preferred surfactants areFlorade FC-430 from Sumitomo 3M, Ltd. and X-70-093 from Shin-EtsuChemical Co., Ltd.

[0201] Pattern formation using the resist composition of the inventionmay be carried out by a known lithographic technique. For example, theresist composition is applied onto a substrate such as a silicon waferby spin coating or the like to form a resist film having a thickness of0.2 to 2.0 μm, which is then pre-baked on a hot plate at 60 to 150° C.for 1 to 10 minutes, and preferably at 80 to 130° C. for 1 to 5 minutes.A patterning mask having the desired pattern is then placed over theresist film, and the film exposed through the mask to an electron beamor to high-energy radiation such as deep-UV rays, an excimer laser, orx-rays in a dose of about 1 to 200 mJ/cm², and preferably about 5 to 100mJ/cm², then post-exposure baked (PEB) on a hot plate at 60 to 150° C.for 1 to 5 minutes, and preferably at 80 to 130° C. for 1 to 3 minutes.Finally, development is carried out using as the developer an aqueousalkali solution, such as a 0.1 to 5% (preferably 2 to 3%) aqueoussolution of tetramethylammonium hydroxide (TMAH), this being done by aconventional method such as dipping, puddling, or spraying for a periodof 0.1 to 3 minutes, and preferably 0.5 to 2 minutes. These steps resultin the formation of the desired pattern on the substrate. Of the varioustypes of high-energy radiation that may be used, the resist compositionof the invention is best suited to fine pattern formation with, inparticular, deep-UV rays having a wavelength of 248 to 193 nm, anexcimer laser, x-rays, or an electron beam. The desired pattern may notbe obtainable outside the upper and lower limits of the above range.

[0202] The resist composition comprising the polymer as a base resinlends itself to micropatterning with electron beams or deep-UV rayssince it is sensitive to high-energy radiation and has excellentsensitivity, resolution, and etching resistance. Especially because ofthe minimized absorption at the exposure wavelength of an ArF or KrFexcimer laser, a finely defined pattern having sidewalls perpendicularto the substrate can easily be formed.

EXAMPLE

[0203] Synthesis Examples and Examples are given below by way ofillustration and not by way of limitation. The abbreviation Mw is aweight average molecular weight, Mn is a number average molecularweight, SEM is scanning electron microscope, and TMAH istetramethylammonium hydroxide.

[0204] Ether compounds and polymers thereof within the scope of theinvention were synthesized by the following procedure.

Synthesis Example 1-1

[0205] Synthesis of 5-(1-hydroxy-5-methoxypentyl)-2-norbornene (Monomer1)

[0206] In 300 g of tetrahydrofuran was dissolved 122.6 g of1-chloro-4-methoxybutane. The solution was added dropwise to 24.3 g ofmetallic magnesium over 2 hours and below 60° C. Agitation was continuedfor 2 hours at room temperature. To the solution, 122.2 g of5-norbornene-2-carbaldehyde was added dropwise over one hour and below50° C. Agitation was continued for one hour at room temperature to drivethe reaction to completion. Then 300 g of water and 44 g of 20% HCl wereadded to the solution, which was agitated. Extraction with 500 g ofhexane gave the organic layer, which was washed with water, dried overanhydrous sodium sulfate, filtered, and concentrated in vacuum. The oilymatter thus obtained was distilled in vacuum, obtaining 158.6 g of5-(1-hydroxy-5-methoxypentyl)-2-norbornene. The yield was 75.4%.

[0207] IR (thin film): νν=3415 (br.), 3057, 2937, 2866, 1458, 1450,1389, 1120, 719 cm⁻¹

[0208]¹H-NMR (300 MHz in CDCl₃) of5-(1-hydroxy-5-methoxypentyl)-2-norbornene (exo form:endo form=45:55):δ=0.46-0.52 (0.55H, ddd, J=11.6, 4.7, 2.5 Hz), 0.88-0.94 (0.45H, ddd,J=11.6, 4.1, 2.5 Hz), 1.19-1.67 (9H, m), 1.70-1.78 (0.55H, ddd, J=11.6,9.4, 3.9 Hz), 1.81-1.89 (0.45H, ddd, J=11.6, 8.8, 3.9 Hz), 1.96-2.09(1H, m), 2.76-3.04 (3H, m), 3.30-3.41 (5H, m) (inclusive of 3.30 (1.65H,s), 3.31 (1.35H, s)), 5.85-5.88 (0.45H, m), 5.97-6.00 (0.55H, m),6.01-6.15 (1H, m)

Synthesis Example 1-2

[0209] Synthesis of 5-(1-acetoxy-5-methoxypentyl)-2-norbornene (Monomer2)

[0210] In 63.3 g of pyridine, 105.2 g of5-(1-hydroxy-5-methoxypentyl)-2-norbornene (Monomer 1) was reacted with61.3 g of acetic anhydride in the presence of 2 g of4-dimethylaminopyridine at room temperature for 10 hours. The reactionwas stopped by adding 30 g of water. Extraction with hexane gave theorganic layer, which was washed with water, dried over anhydrous sodiumsulfate, filtered, and concentrated in vacuum. The oily matter thusobtained was distilled in vacuum, obtaining 122.4 g of5-(1-acetoxy-5-methoxypentyl)-2-norbornene. The yield was 97.0%.

[0211] IR (thin film): ν=3057, 2939, 2868, 1734, 1458, 1373, 1338, 1244,1120, 1020, 723 cm⁻¹

[0212]¹H-NMR (270 MHz in CDCl₃) of5-(1-acetoxy-5-methoxypentyl)-2-norbornene (exo form:endo form=45:55):δ=0.52-0.59 (0.55H, ddd, J=11.7, 4.9, 2.4 Hz), 0.70-0.77 (0.45H, ddd,J=11.7, 4.4, 2.4 Hz), 1.10-1.82 (10H, m), 1.98 (1.35H, s), 2.05 (1.65H,s), 2.15-2.57 (1H, m), 2.76 (2H, br. s), 3.29 (1.65H, s), 3.30 (1.35H,s), 4.29-4.46 (1H, m), 5.85-5.90 (1H, m), 6.11-6.18 (1H, m)

Synthesis Example 1-3

[0213] Synthesis of 5-{2-(2-hydroxy-6-methoxyhexyl)1}-2-norbornene(Monomer 3)

[0214] The procedure of Synthesis Example 1-1 was repeated except that5-acetyl-2-norbornene was used instead of 5-norbornene-2-carbaldehyde.In this way, 5-{2-(2-hydroxy-6-methoxyhexyl)}-2-norbornene wassynthesized in a yield of 74%.

[0215] IR (thin film): ν=3572, 3485 (br.), 3057, 2968, 2939, 2868, 1710,1682, 1570, 1464, 1460, 1373, 1369, 1338, 1294, 1271, 1255, 1238, 1196,1119, 931, 742, 719 cm⁻¹

[0216]¹H-NMR (300 MHz in CDCl₃) of5-{2-(2-hydroxy-6-methoxyhexyl)}-2-norbornene (exo form:endoform=48:52): δ=1.00 (1.44H, s), 1.05-1.16 (2.56H, m) (inclusive of 1.16(1.56H, s)), 1.18-1.63 (9H, m), 1.74-1.86 (1H, m), 2.18-2.25 (1H, m),2.80 (1H, br. s), 2.91 (1H, br. s), 3.31-3.41 (5H, m) (inclusive of 3.31(1.56H, s), 3.32 (1.44H, s)), 6.06-6.10 (1H, m), 6.20-6.24 (1H, m)

Synthesis Example 1-4

[0217] Synthesis of 5-(2-acetoxy-5-methoxypentyl)-2-norbornene (Monomer4)

[0218] The procedure of Synthesis Example 1-1 was repeated except that(5-norbornen-2-yl)acetaldehyde was used instead of5-norbornene-2-carbaldehyde. In this way,5-(2-hydroxy-5-methoxypentyl)-2-norbornene was synthesized in a yield of73%.

[0219] The procedure of Synthesis Example 1-2 was repeated except that5-(2-hydroxy-5-methoxypentyl)-2-norbornene was used instead of5-(1-hydroxy-5-methoxypentyl)-2-norbornene. In this way,5-(2-acetoxy-5-methoxypentyl)-2-norbornene was synthesized in a yield of95%.

[0220] IR (thin film): ν=3057, 2958, 2868, 1736, 1448, 1373, 1244, 1120,1022, 719 cm⁻¹

[0221]¹H-NMR (270 MHz in CDCl₃) of the main isomer (endo form) of5-(2-acetoxy-5-methoxypentyl)-2-norbornene: δ=0.46-0.57 (1H, m),1.12-1.63 (8H, m), 1.78-1.88 (1H, m), 1.93-2.01 (4H, m) (inclusive of2.01 (3H, s)), 2.73 (1H, br. s), 2.78 (1H, br. s), 3.28-3.34 (5H, m)(inclusive of 3.30 (3H, s)), 4.89 (1H, m), 5.85-5.94 (1H, m), 6.07-6.11(1H, m)

Synthesis Example 2-1

[0222] Synthesis of Polymer 1

[0223] In 150 ml of tetrahydrofuran were dissolved 42.1 g of Monomer 1,78.1 g of 2-ethyl-2-norbornyl 5-norbornene-2-carboxylate and 49.0 g ofmaleic anhydride. To the solution was added 1.8 g of2,2′-azobis(2-methylbutyronitrile). The solution was stirred for 15hours at 60° C. and then concentrated in vacuum. The residue wasdissolved in 600 ml of tetrahydrofuran, which was added dropwise to 10liters of n-hexane. The resulting solids were collected by filtration,washed with 10 liters of n-hexane, and vacuum dried for 6 hours at 40°C. There was obtained 86.7 g of a polymer designated Polymer 1 whosestructure is shown below. The yield was 51.2%.

[0224] A GPC analysis of the polymer showed a Mw of 8,100 on apolystyrene basis and a dispersity Mw/Mn of 1.78. On ¹³C-NMR analysis ofthe polymer, the ratio of Monomer 1/2-ethyl-2-norbornyl5-norbornene-2-carboxylate/maleic anhydride was 0.2/0.3/0.5.

Synthesis Examples 2-2 to 2-15

[0225] Synthesis of Polymers 2 to 15

[0226] Polymers 2 to 15 were synthesized by the same procedure as aboveor a well-known procedure.

Example I

[0227] Resist compositions were formulated using inventive polymers asthe base resin and examined for substrate adhesion.

Examples I-1 to I-5 and Comparative Examples 1. 2

[0228] Resist compositions were prepared by using inventive polymers(Polymers 1 to 5) or comparative polymers (Polymers 16 and 17 identifiedbelow) as the base resin, and dissolving the polymer, a photoacidgenerator (designated as PAG1), and a basic compound in a solvent inaccordance with the formulation shown in Table 1. These compositionswere each filtered through a Teflon filter (pore diameter 0.2 μm),thereby giving resist solutions.

[0229] These resist solutions were spin coated ontohexamethyldisilazane-spray coated silicon wafers at 90° C. for 40seconds, then heat treated at 110° C. for 90 seconds to give resistfilms having a thickness of 0.5 μm. The resist films were exposed usingan KrF excimer laser stepper (Nikon Corporation; NA 0.5), then heattreated at 110° C. for 90 seconds, and puddle developed with a solutionof 2.38% TMAH in water for 60 seconds, thereby giving 1:1 line-and-spacepatterns. The wafers as developed were observed under overhead SEM. Theminimum width (μm) of lines left unstripped is the limit of adhesion ofthe resist under test.

[0230] The composition and test results of the resist materials areshown in Table 1.

[0231] The solvents and basic compound used are propylene glycol methylether acetate (PGMEA) and tributyl amine (TBA), respectively. It isnoted that the solvent contained 0.01% by weight of surfactant FloradeFC-430 (Sumitomo 3M). TABLE 1 Basic Limit of Photoacid com- adhe- Resingenerator pound Solvent sion, (pbw) (pbw) (pbw) (pbw) μm Example I-1Polymer 1 PAG 1 TBA PGMEA 0.24 (80) (1) (0.078) (480) I-2 Polymer 2 PAG1 TEA PGMEA 0.23 (80) (1) (0.078) (480) I-3 Polymer 6 PAG 1 TBA PGMEA0.24 (80) (1) (0.078) (480) I-4 Polymer 8 PAG 1 TBA PGMEA 0.22 (80) (1)(0.078) (480) I-5 Polymer 9 PAG 1 TBA PGMEA 0.23 (80) (1) (0.078) (480)Com- 1 Polymer 16 PAG 1 TBA PGMEA >0.50 parative (80) (1) (0.078) (480)Example 2 Polymer 17 PAG 1 TBA PGMEA >0.50 (80) (1) (0.078) (480)

[0232] It is evident from Table 1 that the polymers within the scope ofthe invention have good substrate adhesion.

Example II

[0233] Resist compositions were formulated using inventive polymers andexamined for resolution upon KrF excimer laser exposure.

Examples II-1 to II-21 Evaluation of Resist Resolution

[0234] Resist compositions were prepared by using Polymers 1 to 15 asthe base resin, and dissolving the polymer, a photoacid generator(designated as PAG1 and 2), a dissolution regulator (designated as DRR1to 4), a basic compound, and a compound having a ≡C—COOH group in themolecule (ACC1 and 2) in a solvent in accordance with the formulationshown in Table 2. These compositions were each filtered through a Teflonfilter (pore diameter 0.2 μm), thereby giving resist solutions.

[0235] The solvent and basic compounds used are as follows. It is notedthat the solvent contained 0.01% by weight of surfactant Florade FC-430(Sumitomo 3M).

[0236] PGMEA: propylene glycol methyl ether acetate

[0237] TEA: triethanolamine

[0238] TMMEA: trismethoxymethoxyethylamine

[0239] TMEMEA: trismethoxyethoxymethoxyethylamine

[0240] These resist solutions were spin coated ontohexamethyldisilazane-spray coated silicon wafers at 90° C. for 90seconds, then heat treated at 110° C. for 90 seconds to give resistfilms having a thickness of 0.5 μm. The resist films were exposed usingan KrF excimer laser stepper (Nikon Corporation; NA 0.5), then heattreated at 110° C. for 90 seconds, and puddle developed with a solutionof 2.38% TMAH in water for 60 seconds, thereby giving 1:1 line-and-spacepatterns.

[0241] The wafers as developed were sectioned and observed undersectional SEM. The optimal dose (Eop, mJ/cm²) was defined as the dosewhich provided a 1:1 resolution at the top and bottom of a 0.30 μmline-and-space pattern. The resolution of the resist under evaluationwas defined as the minimum line width (μm) of the lines and spaces thatseparated at the optimal dose. The shape of the resolved resist patternwas examined under a SEM.

[0242] The composition and test results of the resist materials areshown in Table 2. TABLE 2 Photoacid Dissolution Basic Resin generatorregulator compound Solvent Eop, Resolution, Example (pbw) (pbw) (pbw)(pbw) (pbw) mJ/cm² μm Shape II-1 Polymer 1 PAG 1 TEA PGMEA 26.0 0.20rectangular (80) (1) (0.063) (480) II-2 Polymer 2 PAG 1 TEA PGMEA 25.00.21 rectangular (80) (1) (0.063) (480) II-3 Polymer 3 PAG 1 TEA PGMEA23.0 0.22 rectangular (80) (1) (0.063) (480) II-4 Polymer 4 PAG 1 TEAPGMEA 27.0 0.24 rectangular (80) (1) (0.063) (480) II-5 Polymer 5 PAG 1TEA PGMEA 28.0 0.25 rectangular (80) (1) (0.063) (480) II-6 Polymer 6PAG 1 TEA PGMEA 24.0 0.20 rectangular (80) (1) (0.063) (480) II-7Polymer 7 PAG 1 TEA PGMEA 23.0 0.22 rectangular (80) (1) (0.063) (480)II-8 Polymer 8 PAG 1 TEA PGMEA 22.0 0.20 rectangular (80) (1) (0.063)(480) II-9 Polymer 9 PAG 1 TEA PGMEA 22.0 0.21 rectangular (80) (1)(0.063) (480) II-10 Polymer 10 PAG 1 TEA PGMEA 19.0 0.22 rectangular(80) (1) (0.063) (480) II-11 Polymer 11 PAG 1 TEA PGMEA 21.0 0.22rectangular (80) (1) (0.063) (480) II-12 Polymer 12 PAG 1 TEA PGMEA 22.00.23 rectangular (80) (1) (0.063) (560) II-13 Polymer 13 PAG 1 TEA PGMEA22.0 0.24 rectangular (80) (1) (0.063) (560) II-14 Polymer 14 PAG 1 TEAPGMEA 21.0 0.22 rectangular (80) (1) (0.063) (640) II-15 Polymer 15 PAG1 TEA PGMEA 32.0 0.21 rectangular (80) (1) (0.063) (640) II-16 Polymer 6PAG 2 TEA PGMEA 23.0 0.20 rectangular (80) (1) (0.063) (480) II-17Polymer 6 PAG 2 TMMEA PGMEA 24.0 0.20 rectangular (80) (1) (0.118) (480)II-18 Polymer 6 PAG 2 TMEMEA PGMEA 26.0 0.21 rectangular (80) (1)(0.173) (480) II-19 Polymer 8 PAG 2 DRR 1 TEA PGMEA 18.0 0.21rectangular (70) (1) (10) (0.063) (480) II-20 Polymer 8 PAG 2 DRR 2 TEAPGMEA 20.0 0.22 rectangular (70) (1) (10) (0.063) (480) II-21 Polymer 8PAG 2 DRR 3 TEA PGMEA 22.0 0.22 rectangular (70) (1) (10) (0.063) (480)II-22 Polymer 8 PAG 2 DRR 4 TEA PGMEA 22.0 0.20 rectangular (70) (1)(10) (0.063) (480) II-22 Polymer 8 PAG 2 ACC 1 TEA PGMEA 20.0 0.21rectangular (80) (1) (4) (0.063) (480) II-23 Polymer 8 PAG 2 ACC 2 TEAPGMEA 22.0 0.21 rectangular (80) (1) (4) (0.063) (480)

[0243] It is seen from Table 2 that the resist compositions within thescope of the invention have a high sensitivity and resolution upon KrFexcimer laser exposure.

Example III

[0244] Resist compositions were formulated using inventive polymers andexamined for resolution upon ArF excimer laser exposure.

Examples III-1 to III-2 Evaluation of Resist Resolution

[0245] Resist compositions were prepared as in Example II in accordancewith the formulation shown in Table 3.

[0246] The resulting resist solutions were spin coated ontohexamethyldisilazane-spray coated silicon wafers at 90° C. for 90seconds, then heat treated at 110° C. for 90 seconds to give resistfilms having a thickness of 0.5 μm. The resist films were exposed usingan ArF excimer laser stepper (Nikon Corporation; NA 0.55), then heattreated at 110° C. for 90 seconds, and puddle developed with a solutionof 2.38% TMAH in water for 60 seconds, thereby giving 1:1 line-and-spacepatterns.

[0247] The wafers as developed were sectioned and observed undersectional SEM. The optimal dose (Eop, mJ/cm²) was defined as the dosewhich provided a 1:1 resolution at the top and bottom of a 0.25 μmline-and-space pattern. The resolution of the resist under evaluationwas defined as the minimum line width (μm) of the lines and spaces thatseparated at the optimal dose. The shape of the resolved resist patternwas examined under a SEM.

[0248] The composition and test results of the resist materials areshown in Table 3. It is noted that the solvents and basic compounds inTable 3 are as follows. It is noted that the solvent contained 0.01% byweight of surfactant Florade FC-430 (Sumitomo 3M).

[0249] PGMEA: propylene glycol methyl ether acetate

[0250] TEA: triethanolamine

[0251] TMMEA: trismethoxymethoxyethylamine TABLE 3 Photoacid Basic Resingenerator compound Solvent Eop, Resolution, Example (pbw) (pbw) (pbw)(pbw) mJ/cm² μm Shape III-1 Polymer 6 PAG1 (1) TEA PGMEA 17.0 0.16rectangular (80) (0.063) (480) III-2 Polymer 6 PAG2 (1) TMMEA PGMEA 18.00.15 rectangular (80) (0.118) (480)

[0252] It is seen from Table 3 that the resist compositions within thescope of the invention have a high sensitivity and resolution upon ArFexcimer laser exposure.

[0253] Japanese Patent Application No. 2001-008988 is incorporatedherein by reference.

[0254] Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. An ether compound of the following general formula (1):

wherein R¹ is hydrogen or a straight, branched or cyclic alkyl group of1 to 6 carbon atoms, R² is a straight, branched or cyclic alkyl group of1 to 6 carbon atoms, R³ is hydrogen or an acyl or alkoxycarbonyl groupof 1 to 15 carbon atoms in which some or all of the hydrogen atoms onthe constituent carbon atoms may be substituted with halogen atoms, k is0 or 1, m is an integer from 0 to 3, and n is an integer from 3 to
 6. 2.A polymer comprising recurring units of the following general formula(1-1) or (1-2) derived from the ether compound of the above formula (1)and having a weight average molecular weight of 1,000 to 500,000,

wherein k, m, n, and R¹ to R³ are as defined above.
 3. The polymer ofclaim 2 comprising, in addition to the recurring units of formula (1-1),recurring units of the following general formula (2-1):

wherein k is as defined above, R⁴ is hydrogen, methyl or CH₂CO₂R⁶, R⁵ ishydrogen, methyl or CO₂R⁶, R⁶ is a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms, R⁷ is an acid labile group, R⁸ isselected from the class consisting of a halogen atom, a hydroxyl group,a straight, branched or cyclic alkoxy, acyloxy or alkylsulfonyloxy groupof 1 to 15 carbon atoms, and a straight, branched or cyclicalkoxycarbonyloxy or alkoxyalkoxy group of 2 to 15 carbon atoms, inwhich some or all of the hydrogen atoms on constituent carbon atoms maybe substituted with halogen atoms, Z is a single bond or a straight,branched or cyclic (p+2)-valent hydrocarbon group of 1 to 5 carbonatoms, in which at least one methylene may be substituted with oxygen toform a chain-like or cyclic ether or two hydrogen atoms on a commoncarbon may be substituted with oxygen to form a ketone, and p is 0, 1 or2.
 4. The polymer of claim 2 comprising, in addition to the recurringunits of formula (1-1), recurring units of the following generalformulae (2-1) and (3):

wherein Z, k, p and R⁴ to R⁸ are as defined above, and Y is an oxygenatom or NR⁹ wherein R⁹ is a straight, branched or cyclic alkyl group of1 to 6 carbon atoms.
 5. The polymer of claim 2 comprising, in additionto the recurring units of formula (1-1), recurring units of thefollowing general formula (4) alone or in combination with recurringunits of the following general formula (2-1), and recurring units of thefollowing general formula (3):

wherein Y, Z, k, p and R⁴ to R⁹ are as defined above.
 6. The polymer ofclaim 2 comprising, in addition to the recurring units of formula (1-2),recurring units of the following general formula (2-2):

wherein Z, k, p and R⁴ to R⁸ are as defined above.
 7. A resistcomposition comprising the polymer of claim
 2. 8. A process for forminga resist pattern comprising the steps of: applying the resistcomposition of claim 7 onto a substrate to form a coating, heat treatingthe coating and then exposing it to high-energy radiation or electronbeams through a photo mask, and optionally heat treating the exposedcoating and developing it with a developer.